<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="text" id="d1">
<input type="text" id="d2">
<input type="button" value="加" onclick="f(1)">
<input type="button" value="减" onclick="f(2)">
<input type="button" value="乘" onclick="f(3)">
<input type="button" value="除" onclick="f(4)">
<div>
    结果<span></span>
</div>
<script>
    function f(x) {
        let span =document.querySelector("span");
        switch (x){
            case 1:
                span.innerText = d1.value*1 + d2.value*1;
                break;
            case 2:
                span. innerText= d1.value-d2.value;
                break;
            case 3:
                span. innerText=d1.value*va.value;
                break;
            case 4:
                span.innerText =d1.value/d2.value;
               break;
        }
    }
</script>
</body>
</html>